1. Field of the Invention
This invention relates to a surgical instrument for causing a member to penetrate into an organ or body part to a desired depth which is within a desired distance from a remote face of the organ or body part.
2. Description of the Prior Art
Certain processes for example, eye surgery, require that a knife or blade be made to penetrate into the cornea to an accurately controllable depth. In such processes the knife blade, is caused to protrude by a preset amount from a guard resting on the outer surface of the eye ball to be incised.
Great care must be taken not to carry the incision beyond the depth of the cornea since otherwise irreparable damage will result.
Before performing such an operation a surgeon will map out the thickness of the cornea in different places using an ultrasonic tool. Then using the map the surgeon will effect a number of incisions changing the extent of protrusion of the knife between strokes according to the thickness indicated on the map. The process is a highly complex and laborious one and errors are still likely to occur.
It is an aim of the present invention to provide an improved tool for facilitating such processes.